What is a composite key?

What is a composite key?

• A. Contains only one simple key
• B. Contains one compound key and at least one other attribute
• C. Only refers to unique attributes
• D. Can have multiple primary keys

Answer: (B)

A composite key is defined as a key that consists of two or more attributes that uniquely identify an entity in a database. This means that no single attribute can uniquely identify the record on its own, but when combined with other attributes, they form a unique identifier for that record. Thus, the correct choice highlights that a composite key includes at least one compound key, which refers to the combination of these multiple attributes, and at least one additional attribute that helps ensure uniqueness. In database design, composite keys are particularly useful in scenarios where individual attributes may have duplicate values but the combination of those attributes creates a unique record, thereby maintaining data integrity. Understanding composite keys is crucial for database normalization and for ensuring that entities within a database can be reliably accessed and identified. In contrast, while other options might touch on aspects of keys in a database, they do not accurately encompass the definition and functionality of a composite key. For instance, a simple key is just one unique attribute, which does not qualify as a composite key. Attributes that are unique on their own might refer to primary keys, but they do not indicate the combination necessary for a composite key.

A composite key is defined as a key that consists of two or more attributes that uniquely identify an entity in a database. This means that no single attribute can uniquely identify the record on its own, but when combined with other attributes, they form a unique identifier for that record. Thus, the correct choice highlights that a composite key includes at least one compound key, which refers to the combination of these multiple attributes, and at least one additional attribute that helps ensure uniqueness.

In database design, composite keys are particularly useful in scenarios where individual attributes may have duplicate values but the combination of those attributes creates a unique record, thereby maintaining data integrity. Understanding composite keys is crucial for database normalization and for ensuring that entities within a database can be reliably accessed and identified.

In contrast, while other options might touch on aspects of keys in a database, they do not accurately encompass the definition and functionality of a composite key. For instance, a simple key is just one unique attribute, which does not qualify as a composite key. Attributes that are unique on their own might refer to primary keys, but they do not indicate the combination necessary for a composite key.